[PATCHv3 08/12] pixfmt-compressed.rst: improve H264/HEVC/MPEG1+2/VP8+9 documentation
From: Hans Verkuil <hidden>
Date: 2019-08-15 14:45:07
Subsystem:
documentation, the rest · Maintainers:
Jonathan Corbet, Linus Torvalds
The existing documentation was incorrect and did not correspond to how actual codec drivers implemented this. Update the documentation to explicitly specify what is actually expected. Signed-off-by: Hans Verkuil <redacted> --- .../media/uapi/v4l/pixfmt-compressed.rst | 36 +++++++++++++++---- 1 file changed, 30 insertions(+), 6 deletions(-)
diff --git a/Documentation/media/uapi/v4l/pixfmt-compressed.rst b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
index f52a7b67023d..9bb4a172a660 100644
--- a/Documentation/media/uapi/v4l/pixfmt-compressed.rst
+++ b/Documentation/media/uapi/v4l/pixfmt-compressed.rst@@ -41,7 +41,12 @@ Compressed Formats - ``V4L2_PIX_FMT_H264`` - 'H264' - - H264 video elementary stream with start codes. + - H264 Access Unit. + The decoder expects one Access Unit per buffer. + The encoder generates one Access Unit per buffer. + If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM`` + then the decoder has no requirements since it can parse all the + information from the raw bytestream. * .. _V4L2-PIX-FMT-H264-NO-SC: - ``V4L2_PIX_FMT_H264_NO_SC``
@@ -86,12 +91,20 @@ Compressed Formats - ``V4L2_PIX_FMT_MPEG1`` - 'MPG1' - - MPEG1 video elementary stream. + - MPEG1 Picture. Each buffer starts with a Picture header, followed + by other headers as needed and ending with the Picture data. + If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM`` + then the decoder has no requirements since it can parse all the + information from the raw bytestream. * .. _V4L2-PIX-FMT-MPEG2: - ``V4L2_PIX_FMT_MPEG2`` - 'MPG2' - - MPEG2 video elementary stream. + - MPEG2 Picture. Each buffer starts with a Picture header, followed + by other headers as needed and ending with the Picture data. + If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM`` + then the decoder has no requirements since it can parse all the + information from the raw bytestream. * .. _V4L2-PIX-FMT-MPEG2-SLICE: - ``V4L2_PIX_FMT_MPEG2_SLICE``
@@ -132,7 +145,9 @@ Compressed Formats - ``V4L2_PIX_FMT_VP8`` - 'VP80' - - VP8 video elementary stream. + - VP8 compressed video frame. The encoder generates one + compressed frame per buffer, and the decoder requires one + compressed frame per buffer. * .. _V4L2-PIX-FMT-VP8-FRAME: - ``V4L2_PIX_FMT_VP8_FRAME``
@@ -157,12 +172,19 @@ Compressed Formats - ``V4L2_PIX_FMT_VP9`` - 'VP90' - - VP9 video elementary stream. + - VP9 compressed video frame. The encoder generates one + compressed frame per buffer, and the decoder requires one + compressed frame per buffer. * .. _V4L2-PIX-FMT-HEVC: - ``V4L2_PIX_FMT_HEVC`` - 'HEVC' - - HEVC/H.265 video elementary stream. + - HEVC/H.265 Access Unit. + The decoder expects one Access Unit per buffer. + The encoder generates one Access Unit per buffer. + If :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM`` + then the decoder has no requirements since it can parse all the + information from the raw bytestream. * .. _V4L2-PIX-FMT-FWHT: - ``V4L2_PIX_FMT_FWHT``
@@ -170,6 +192,8 @@ Compressed Formats - Video elementary stream using a codec based on the Fast Walsh Hadamard Transform. This codec is implemented by the vicodec ('Virtual Codec') driver. See the codec-fwht.h header for more details. + :ref:`VIDIOC_ENUM_FMT` reports ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM`` + since the decoder can parse all the information from the raw bytestream. * .. _V4L2-PIX-FMT-FWHT-STATELESS: - ``V4L2_PIX_FMT_FWHT_STATELESS``
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2.20.1